1. Field of the Invention
The invention relates generally to the field of measuring instrumentation used in wellbores drilled through subsurface rock formations. More specifically, the invention relates to structures usable as housings for such instrumentation.
2. Background Art
Wellbore-deployed instrumentation includes various sensing devices disposed in a housing or “sub” coupled within a conduit called a “drill string” suspended in a wellbore for the drilling of such wellbore. A drill string is a length of pipe generally assembled from segments (“joints”) threadedly coupled end to end and having a drill bit at the lower end of the drill string. Drilling is performed by rotating and axially urging the drill bit to the bottom of the wellbore to extend the length of the wellbore. Wellbore deployed instrumentation also includes various sensing devices disposed in housing(s) moved along the interior of the wellbore using armored electrical cable, “slickline” or other conveyance deployed from the surface. The various sensing devices within the instruments are used to impart certain types of energy into the rock formations outside the wellbore, and to detect response of the formations to such imparted energy.
Irrespective of the type of sensor or the type of conveyance of the various instruments along the interior of the wellbore, a common feature of such wellbore instrumentation is that electronic components and sensing elements are disposed in a pressure-sealed or pressure balanced housing that excludes wellbore fluid under pressure from entering the interior of such housing. Housings made from steel, stainless, steel, non-magnetic metal alloy (e.g., monel), for example, are used because of their high tensile strength and resistance to crushing under hydrostatic pressure of fluid within the wellbore. However, such housings are heavy, and can be expensive to make. Further, it is frequently necessary to mount certain sensing elements next to energy transparent “windows” or within recesses machined into the exterior wall of the housing in order to be able to impart energy into the rock formations surrounding the well and to detect the formation response therefrom. Still other examples of wellbore instrumentation may include electromagnetic transmitters and/or receivers in the form of solenoid, toroidal, planar, tilted, triaxial, etc coils disposed on an electrically conductive mandrel.
Accordingly, there exists a need for high temperature, high pressure, abrasive resistant, chemically resistant, lighter weight, strong, energy transparent materials from which to make wellbore instrument housings.